#ifndef ARENA_H
#define ARENA_H

#include <stdint.h>

typedef uint8_t err_t;

struct arena {
	uint8_t *data;
	size_t cur;
	size_t cap;
};

struct void_p_err_t {
	void *ptr;
	err_t err;
};

struct arena_void_p_err_t {
	struct arena arena;
	void *ptr;
	err_t err;
};

struct arena_err_t {
	struct arena arena;
	err_t err;
};

enum arena_err {
	ARENA_ERR_OK = 0,
	ARENA_ERR_MALLOC_FAIL,
	ARENA_ERR_HIT_CAP
};

struct arena_err_t arena_create(size_t cap);
err_t arena_destroy(struct arena arena);

struct void_p_err_t arena_alloc(struct arena *arena, size_t size);
struct arena_void_p_err_t arena_alloc_pure(struct arena arena, size_t size);

err_t arena_forget(struct arena *arena);
struct arena_err_t arena_forget_pure(struct arena arena);

#if defined(ARENA_IMP) || defined(IMP)

#include <stdlib.h>

struct arena_err_t
arena_create(size_t cap)
{
	void *data = calloc(cap, sizeof(uint8_t));

	if ( data == NULL ) {
		return (struct arena_err_t) { .err = ARENA_ERR_MALLOC_FAIL };
	}

	struct arena arena = {
		.data = data,
		.cap = cap,
		.cur = 0
	};

	return (struct arena_err_t) { .arena = arena, .err = ARENA_ERR_OK };
}

err_t
arena_destroy(struct arena arena)
{
	free(arena.data);
	return ARENA_ERR_OK;
}



struct void_p_err_t
arena_alloc(struct arena *arena, size_t size)
{
	if ( arena->cur + size >= arena->cap ) {
		return (struct void_p_err_t) {
			.ptr = NULL,
			.err = ARENA_ERR_HIT_CAP
		};
	}

	void * ptr = (void *) (arena->data + arena->cur);
	arena->cur += size;

	return (struct void_p_err_t) {
		.ptr = ptr,
		.err = ARENA_ERR_OK
	};
}


struct arena_void_p_err_t
arena_alloc_pure(struct arena arena, size_t size)
{
	struct void_p_err_t vpet = arena_alloc(&arena, size);
	return (struct arena_void_p_err_t) {
		.arena = arena,
		.ptr = vpet.ptr,
		.err = vpet.err
	};
}

err_t
arena_forget(struct arena *arena)
{
	arena->cur = 0;
	return ARENA_ERR_OK;
}

struct arena_err_t
arena_forget_pure(struct arena arena)
{
	err_t err = arena_forget(&arena);
	return (struct arena_err_t) { .arena = arena, .err = err };
}

#endif	/* ARENA_IMP || IMPLEMENTATIONS */

#endif	/* ARENA_H */